An overvoltage protection circuit is a circuit which protects electronics from excessive voltage which could potentially damage or destroy electronic components. Over voltage protection circuits typically protect downstream circuitry from damage due to detected excessive voltage. One common application for overvoltage protection is in a mobile device such as a cell phone or personal computer. When such mobile devices are connected to a power source, large transient voltages are often generated at the instant power is applied to the device. In addition to transients, sometimes devices can be connected to improper power sources where the voltage output of the power source exceeds the input requirements of the mobile device. In either overvoltage scenario, overvoltage protection circuits inside the mobile devices can engage when an overvoltage condition is detected in order to limit the voltage to the device.
Typical overvoltage protection circuits attempt to clamp the output voltage from the power source to a predetermined voltage level that can be defined by a reference voltage input to the protection circuit. In some conventional overvoltage clamping circuits, multiple reference voltages are employed at the input to the clamping circuits in an attempt to provide hysteresis in the circuit and hence tailor the response of the clamping circuit. Such attempts utilizing multiple reference voltages typically led to an undesirable amount of ripple voltage at the output of the protection circuit.